Phone claims it's rooted?

I have a Fascinate and I was running rooted 2.1, didn't mess with it too much I just wanted to install Barnacle/Titanium Backup and get rid of some of the bloatware. When I finally got around to installing 2.2 I forgot to unroot the phone first and had to factory reset it thanks to some app compatibility issues. Now I'm running unrooted 2.2 but superuser is still installed, I tried running Z4Root but it says the phone is already rooted (presumably because SU is still installed), when I try to root or unroot it gets as far as "acquiring root shell" then the phone vibrates once, the application closes itself, and then it vibrates twice. How can I re-root?